JP2914803B2 - Semiconductor laser light source device and laser light scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser light source device and a laser beam scanning device. In recent years, semiconductor lasers have been used as light sources for devices using laser light, such as bar code readers, laser printers, and optical disk readers, instead of gas lasers conventionally used. Advantages of using a semiconductor laser as a light source include that the device can be made smaller than a gas laser, and that a reduction in price due to the mass production effect of the semiconductor laser can be expected. In addition, a high-performance and small-sized device has been developed by using a hologram in a device using laser light.

[0002]

2. Description of the Related Art A bar code scanner using a semiconductor laser in a laser beam scanning device using a hologram will be described with reference to FIG. First, the laser light emitted from the semiconductor laser 15 is scanned by the polygon mirror 19.
The scanning light is split and deflected by the scanning line split mirror 16 and is incident on the hollow window 20. Holograms corresponding to each scanning line (scanning light) (12, 13, 14) are formed on the hollow window 20. The scanning line is deflected in a predetermined direction by each hologram, and emitted out of the apparatus from a reading window (LCR). When one of the scanning patterns formed on the reading window crosses (passes) the bar code, the signal light corresponding to the bar code label is reflected. This signal light is collected on the photodetector 18 and the bar code is read.
In a barcode scanner, increasing the amount of signal
Also, improving the reading resolution leads to an improvement in the reading performance of the device.

[0003]

However, when a semiconductor laser is used as a light source, a mode hop phenomenon (oscillation wavelength changes with temperature and light output) peculiar to the semiconductor laser.
Is a problem. The state of the oscillation wavelength at the time of mode hop will be described with reference to FIG. When the temperature rises or the optical output (operating current) changes, the state of FIG. 3A (oscillation wavelength λ _i ) to the state of FIG. 3B (λ _i and λ _{i + 1} compete and one oscillation wavelength occurs). (C is not determined), the state of (C) (oscillation wavelength λ _{i + 1} )
Move on to

When the wavelength of the hologram incident light changes, FIG.
The diffraction angle changes as follows. There is no problem in the case of FIG. 3A or FIG. 3C, but when the oscillation mode is in a competitive state as in FIG. 3B, the light indicated by the solid line and the broken line in FIG. Will be. In this state, the effective beam diameter becomes large. That is, the reading resolution of the apparatus is reduced because the reading resolution is reduced.

For this reason, there has been proposed a method in which the device is provided with a function of detecting the oscillation mode of the semiconductor laser, and when a mode conflict is detected, the output of the semiconductor laser is changed to stabilize the oscillation mode. However, in the above method, there is a problem that stable performance of the device cannot be expected because the output of the laser beam emitted from the device is suddenly changed.

Accordingly, it is an object of the present invention to facilitate mode control of laser light emitted from a semiconductor laser and to prevent two-wavelength output even if the wavelength slightly changes.

[0007]

According to the present invention, there is provided a laser light source for irradiating a laser beam, a control unit for controlling the output of the laser light source, a scanning unit for scanning the laser beam at a predetermined period, In a laser beam scanning device having a hologram that diffracts a laser beam, provided in an optical path,
The control unit sets a predetermined time in a timer so as to prevent contention of the oscillation mode of the laser light source, and sets an output of the timer.
Increase or decrease the laser output step by step
When scanning the laser output, the laser output changes
There is provided a laser beam scanning device which performs control so as to wait for switching of the scanning line.

In another aspect of the present invention, a laser light source for irradiating a laser beam, a control unit for controlling the output of the laser light source, a scanning unit for scanning the laser beam at a predetermined cycle, In a laser beam scanning device having a hologram that diffracts a laser beam, provided in an optical path,
The control unit controls each of the scanning lines so that the light output of each of the scanning lines becomes constant so as to prevent the oscillation mode competition of the laser light source.
The laser output of the light source is changed in synchronization with the
Synchronization is achieved by installing a detector at the
There is provided a laser light scanning device which controls so as to output when light is detected .

[0009]

According to the present invention, since the oscillation mode of the semiconductor laser is detected and the output is not suddenly changed immediately when the mode competition is detected, stable operation of the device can be expected.

[0010]

FIG. 9 is a block diagram of an apparatus for carrying out an embodiment of the present invention, and FIG. 2 shows a configuration of a barcode scanner as an optical unit of the apparatus. First, when the main power supply 41 is turned on, power is supplied to the main printed board 42 and the laser unit 43, the laser power is turned on under the control of the main printed board 42, and the laser diode (LD) emits laser light.

As shown in FIG. 2, the radiated light from the laser diode 15 passes through a hole in the condenser mirror 17, reaches a polygon mirror 19 rotated by a motor, is reflected by three scanning line split mirrors 16, and Each is output as an L, C, or R scan line via a hologram. The three scanning lines are provided so that they can be detected satisfactorily irrespective of the position of the bar-coded object, and the number of scanning lines is not limited to three. The laser beam emitted from the upper portion of the bar code scanner shown in FIG. 2 hits the bar code to be detected, and the scattered light is reflected and follows the reverse of the above-mentioned path. Mirror 19
The light is condensed on the condensing mirror 17 through the optical sensor 18 and detected by the photodetector 18.

The optical signal detected by the photodetector 18 is processed by an A / D conversion circuit and a demodulation circuit of the main printed board 42 so that a bar code can be decoded. The decrypted data is P
It is supplied to an OS system or the like.

In the first embodiment of the present invention, the timer is set to, for example, a certain time ΔT, and the laser output is stepped up or down every time the timer outputs. At this time, when the laser output is used by scanning, the change in the laser output is performed until the scanning line is switched. The reason for this is that if the output is changed without synchronizing with the scanning line switching, it cannot be distinguished from the change in the reflected light when reading the barcode or the change in the output of the laser diode due to the change in the amount of light accompanying the output change. This is because normal barcode reading is inhibited.

The control steps of the first embodiment will be described with reference to the flowchart of FIG. First, in step 1 (S1), it is detected whether or not the current scanning line is the R scanning line.
The process proceeds to step S7, where the laser light amount is set to r. In step S8, the process waits until there is a trigger of the C scanning line.
If the current scan line is not the R scan line in S1, the process proceeds to S2. If the scan line is the L scan line, the process proceeds to S5. If the scan line is not the L scan line, the process proceeds to S3. S
In 5, the light amount is set to 1 (ell), and the process proceeds to S6. In S3, the light amount is set to c, and then the process proceeds to S4, and waits for the trigger of the L scanning line, waits for the trigger of L, and proceeds to S5. S
At 6, the process waits for a trigger of the R scanning line, and the process proceeds to S7 by the R trigger. In this way, the amount of laser light can be set for each scanning line.

The above-described control can be executed by using each element shown in FIG. A signal synchronized with the L, C, and R scanning lines is obtained by a rotation position detection signal synchronized with a motor for rotating the polygon mirror (it can be detected by a detector provided at an end of the scanning line dividing mirror). The power is supplied to the control unit of the LD control unit, and the LD driver is driven to control the light amount of the LD (laser diode).

The second embodiment will be described by taking a bar code scanner using a hologram as an example. FIG. 5 shows an example of the time on the horizontal axis and an example of the optical output of each scanning line emitted from the scanner on the vertical axis. With the rotation of the polygon mirror, L.P.
C. When the R scanning lines are emitted, the hologram corresponding to each scanning line has a difference in characteristics (diffraction efficiency) due to a difference in diffraction direction. Therefore, even if the laser output of the light source is constant, the light output differs depending on the scanning line as shown in FIG. If the output is different for each scanning line, the reflected light from the bar code changes for each scanning line, so that a difference in reading performance occurs between the scanning lines. In this embodiment, the laser output of the light source is changed in synchronization with each scanning line as shown in FIG. 6 so that the light output of each scanning line becomes constant. Synchronization with the scanning line can be performed by providing a detector at the boundary of the scanning line dividing mirror and obtaining a signal output when laser light is detected. In this way, there is no variation in the light quantity of a plurality of scanning lines unlike the conventional device, and there is no difference in the light output of each scanning line emitted from the device as shown in FIG. It becomes possible. When the above embodiment is realized by a hologram disk, the laser output of the light source may be changed for each hologram of each facet.

In the above-described embodiment, the oscillation mode detection function is used to periodically change the laser oscillation output by controlling the oscillation circuit of the semiconductor laser in synchronization with the motor that rotates the detector or the polygon mirror. Although it is not necessary to provide the oscillation mode detection function as the third embodiment, the laser output is not changed immediately after the multi-mode is detected, but is output when the multi-mode is detected and switched to the next scanning line. Can also be changed.

In this case, as the oscillation mode detector, for example, the device described in the specification of Japanese Patent Application No. 3-179611 can be used. It is possible to change the light amount of the laser diode corresponding to the scanning line by using the control of the first embodiment.

In the above embodiment, the laser output is changed stepwise when the scanning line is switched. However, the laser output may be changed in an analog manner with a gentle change curve as shown in FIG. In the fourth embodiment, the control steps are shown by the flowchart of FIG. First, in step 11 (S11), the output of the laser diode is set to an initial value, and then in S12, the timer is set to T ₀ (for example, 30).
Set seconds), the process proceeds to step S15 when S13 and reduced by 1 second at S14 T ₀ becomes 0, detects the output current of the laser diode, adding or subtracting a predetermined value to the detected value in S16 To drive the laser diode to return to S12. In this way, for example, the output of the predetermined value can be added or subtracted every 30 seconds, and by appropriately selecting the predetermined value, the output change as shown in FIG. 8 can be obtained with a smooth analog curve. it can.

FIG. 13 is a partial block diagram showing circuit elements for controlling the fourth embodiment. It is almost the same as FIG. 11, except that a transmitter is provided in the control unit for obtaining an analog signal. The output of the laser diode is controlled according to the output of the transmitter.

[0021]

According to the present invention, mode control of laser light emitted from a semiconductor laser can be facilitated,
It is possible to reduce problems caused by a mode hop phenomenon in a laser light source device using a laser diode.

[Brief description of the drawings]

FIG. 1 is a flowchart of control steps according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a barcode scanner using the present invention.

FIG. 3 is a diagram illustrating a mode hop phenomenon of a semiconductor laser.

FIG. 4 is a diagram illustrating a problem of a barcode scanner due to a mode hop.

FIG. 5 is a diagram for explaining that an output difference occurs due to a characteristic difference between scanning lines in a barcode scanner.

FIG. 6 is a diagram showing a laser output of the apparatus according to the second embodiment of the present invention.

FIG. 7 is a diagram showing a scanning line output corresponding to the laser output of FIG. 6;

FIG. 8 is a diagram illustrating a laser output of the device of the fourth embodiment.

FIG. 9 is a block diagram illustrating an example of an apparatus according to an embodiment of the present invention.

FIG. 10 is a flowchart showing control steps according to the first embodiment of the present invention.

FIG. 11 is a partial block diagram of an apparatus for performing the first embodiment of the present invention.

FIG. 12 is a flowchart showing control steps according to a fourth embodiment of the present invention.

FIG. 13 is a partial block diagram of an apparatus for performing a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Bar code 12 ... R scanning line 13 ... L scanning line 14 ... C scanning line 15 ... Semiconductor laser 16 ... Scanning line division mirror 17 ... Condensing mirror 18 ... Detector 19 ... Polygon mirror 20 ... Hollow window 41 ... Main power supply 42: Main printed board 43: Laser unit 44: Optical unit 45: Bar code label

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification symbol FI H04N 1/113 H04N 1/23 103Z 1/23 103 1/04 104A (72) Inventor Hironori Yoshikawa Nakagawa-ku, Kawasaki City, Kanagawa Prefecture 1015 Odanaka Fujitsu Limited (56) References JP-A-4-32221 (JP, A) JP-A-2-58019 (JP, A) JP-A-63-81317 (JP, A) JP-A-61- 175656 (JP, A) JP-A-63-199477 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01S 3/18 G02B 26/10 102 G06K 7/10 H01S 3/101 H04N 1/113 H04N 1/23 103

Claims (3)

(57) [Claims] 1. A laser light source for irradiating a laser beam, a control unit for controlling an output of the laser light source, a scanning unit for scanning the laser beam at a predetermined cycle, and a laser beam provided in an optical path of the laser beam. A hologram that diffracts the laser light, wherein the control unit sets a predetermined time in a timer so as to prevent the oscillation mode competition of the laser light source , and outputs the output of the timer.
Increase or decrease the laser output step by step
When scanning the laser output, the laser output changes
A laser light scanning device, wherein the laser beam scanning device is controlled so as to wait for switching of the scanning line. 2. A laser light source for irradiating a laser beam, a control unit for controlling an output of the laser light source, a scanning unit for scanning the laser beam at a predetermined cycle, and a laser beam provided in an optical path of the laser beam. A hologram that diffracts the laser light, wherein the control unit controls each scanning line so that the optical output of each scanning line is constant so as to prevent the oscillation mode competition of the laser light source.
The laser output of the light source is changed in synchronization with the
Synchronization is achieved by installing a detector at the
A laser light scanning device, which controls so as to output when light is detected . 3. The laser beam scanning device according to claim 1, further comprising :
Comprising an oscillation mode detection unit for detecting the oscillation mode of light, when the oscillation mode detection unit detects the mode competition of the oscillation mode, the control unit by switching the point of subsequent scan lines
Laser beam scanning apparatus according to claim 2, characterized in that <br/> controlling the laser light source so as to vary the output of the laser light source.